The fabrication of articles of plastic sheet materials such as balloons, bags, bladders and other such types of containers, using heated dies for shaping the plastic sheet, involves thermal cutting, staking and forming operations which are performed at different temperatures. Because of the different temperatures, the use of either a single-piece die or a sectionalized die for performing these operations simultaneously is not obviously indicated, particularly where the different hot die functions must occupy positions in close proximity to one another, because of heat energy transferred among the die sections by thermal conductivity, radiation, and convection. Staking and cutting operations are usually closely spaced, being performed at the peripheral edge of a container. With some films the staking temperatures may be 300.degree. F.-400.degree. F. and the adjacent cutting or trimming temperatures may be 600.degree. F. In another area of the die adjacent staking and film blowing (or vacuum forming or push forming) operations may be required. Here again, there are significant differences in temperatures, the film blowing temperature usually being higher than the staking temperature. The thermal isolation of these different temperature zones, either in a single piece or integrated die structure, requires provision for blocking thermal energy flow from the higher temperature zones into the lower temperature zones to prevent overheating a lower temperature zone which will cause a malfunction.